1. Field of Invention
This invention pertains to the navigation of aircraft, and particularly to method and apparatus of facilitating the landing of aircraft in inclement weather and/or low visibility conditions.
2. Prior Art and Other Considerations
Nowadays the runways at most commercial airports have ground based transmitters which emit radio wave runway signals useful for navigating an aircraft to a destination runway. Among the runway signals are a glide slope signal, a localizer signal, an outer marker signal, and an middle marker signal.
The ground based transmitters for the runway signals are located according to predetermined convention. The outer marker signal is directed essentially upwardly from the ground in a vertical direction at a horizontal distance of between about four miles to about seven miles from the near end of the runway. Similarly, the middle marker signal is broadcast at a horizontal distance of about three thousand feet from the runway. The glide slope signal is directed (at an angle to the horizontal) along the desired approach path to the runway. The localizer signal is directed out from the runway centerline to provide inbound course guidance.
Since about 1948, most aircraft equipped for instrument flight have receivers which sense the runway signals and send electrical signals to various indicators in the aircraft cockpit. For example, when the outer marker signal is received, an outer marker light (usually blue) is momentarily illuminated in the cockpit. Likewise, when the middle marker signal is received, a middle marker light (usually amber) is momentarily illuminated in the cockpit.
The localizer and glide slope signals are represented by a cross-pointer instrument in the cockpit. The cross-pointer instrument is generally a circular gauge which depicts the aircraft orientation by crosshairs. As the orientation of the aircraft changes, the crosshairs move accordingly. The vertical crosshair shows localizer deviation; the horizontal crosshair shows glideslope deviation.
When landing an aircraft, the pilot must continually monitor the cross-pointer. In addition, the pilot must monitor an intimidating number of other dials, gauges, displays, readouts and needles (including the marker signal lights). Even a seasoned pilot requires several seconds to scan the complex instrumentation in the aircraft. With the specific information gleaned from each instrument, the pilot must synthesize the information to form an instantaneous composite mental picture of the aircraft approach.
In addition to the instrument scan, the pilot must continually refer to a written approach chart such as that published by the Jeppesen Company (e.g., a "Jepp Chart"). The approach chart provides a map of the airport vicinity and prescribes a specific approach procedure for the destination runway. Every ILS airport has several unique approach charts for each runway, and the approach charts are revised monthly. Pilots typically carry in the cockpit several volumes of approach charts.
From the foregoing, it can be understood that instrument landing is inefficient and difficult. Instrument landing requires considerable guess-work by the pilot, during a critical period of time in which many other cockpit functions must be performed. Accurate interpretation of the cross-pointer is difficult enough, but the pilot must also interrogate and interpolate many other instruments in order to determine aircraft attitude, location, and other critical flight conditions.
Low visibility landings are difficult since a pilot loses his natural ability to orient himself and the aircraft to external stimuli (i.e., a visible natural horizon). Without visual orientation stimuli through the window, the pilot cannot define or affirm his positional or attitudinal situation. Rather, the pilot must individually interrogate numerous mechanical instruments; mentally store the information; and, assemble the results to formulate a composite mental picture of the overall situation. Since the composite picture requires considerable interpretation and calculation of component data, it is virtually obsolete by the time it is developed.
Under these circumstances, an efficient translation process is difficult. When data translation is inefficient, a pilot will find himself merely reacting to situational circumstances, rather than creating the desired flight situation. This dangerous phenomenon is commonly referred to as "lagging behind the aircraft." The term "cockpit overload" refers to being overwhelmed when rescanning multiple instruments. This overload of information is the leading cause of accidents and fatalities in aviation.
The prior art has attempted to enhance the instrument landing process. For example, CRT "sky maps" are commercially available for electronically displaying two dimensional airport vicinity maps for enroute navigation and flight planning.
U.S. Pat. No. 3,784,969 to Wilckens et al. discloses an aircraft landing display apparatus which provides guidance information in pictorial form. The apparatus includes a CRT which displays a generic runway in a "channel" representation, with the perspective appearance of the channel depending upon the position of the aircraft.
However, the prior art has failed to provide method and apparatus for utilizing aircraft on-board sensors for generating a customized display for a destination runway (as opposed to a generic runway representation), with the runway dimensions being accurately depicted. Nor does the prior art augment a runway display with landing information locationally keyed with reference to the customized display.
Accordingly, it is an object of the present invention to provide a system for enhancing the safety of aircraft instrument landings.
An advantage of the present invention is the provision of a system for facilitating aircraft navigation which provides a customized display for a destination runway.
Another advantage of the present invention is the provision of a system for facilitating aircraft navigation which provides a customized display for a destination runway which additionally provides landing information locationally keyed with reference to the customized display.
A further advantage of the present invention is the provision of a relatively inexpensive and easily operable system.